InterPregGen: genetic studies of pre-eclampsia in three continents

Genetic Associations of Circulating Cardiovascular Proteins With Gestational Hypertension and Preeclampsia

Importance

Hypertensive disorders of pregnancy (HDPs), including gestational hypertension and preeclampsia, are important contributors to maternal morbidity and mortality worldwide. In addition, women with HDPs face an elevated long-term risk of cardiovascular disease.

Objective

To identify proteins in the circulation associated with HDPs.

Design, Setting, and Participants

Two-sample mendelian randomization (MR) tested the associations of genetic instruments for cardiovascular disease-related proteins with gestational hypertension and preeclampsia. In downstream analyses, a systematic review of observational data was conducted to evaluate the identified proteins' dynamics across gestation in hypertensive vs normotensive pregnancies, and phenome-wide MR analyses were performed to identify potential non-HDP-related effects associated with the prioritized proteins. Genetic association data for cardiovascular disease-related proteins were obtained from the Systematic and Combined Analysis of Olink Proteins (SCALLOP) consortium. Genetic association data for the HDPs were obtained from recent European-ancestry genome-wide association study meta-analyses for gestational hypertension and preeclampsia. Study data were analyzed October 2022 to October 2023.

Exposures

Genetic instruments for 90 candidate proteins implicated in cardiovascular diseases, constructed using cis-protein quantitative trait loci (cis-pQTLs).

Main Outcomes and Measures

Gestational hypertension and preeclampsia.

Results

Genetic association data for cardiovascular disease-related proteins were obtained from 21 758 participants from the SCALLOP consortium. Genetic association data for the HDPs were obtained from 393 238 female individuals (8636 cases and 384 602 controls) for gestational hypertension and 606 903 female individuals (16 032 cases and 590 871 controls) for preeclampsia. Seventy-five of 90 proteins (83.3%) had at least 1 valid cis-pQTL. Of those, 10 proteins (13.3%) were significantly associated with HDPs. Four were robust to sensitivity analyses for gestational hypertension (cluster of differentiation 40, eosinophil cationic protein [ECP], galectin 3, N-terminal pro-brain natriuretic peptide [NT-proBNP]), and 2 were robust for preeclampsia (cystatin B, heat shock protein 27 [HSP27]). Consistent with the MR findings, observational data revealed that lower NT-proBNP (0.76- to 0.88-fold difference vs no HDPs) and higher HSP27 (2.40-fold difference vs no HDPs) levels during the first trimester of pregnancy were associated with increased risk of HDPs, as were higher levels of ECP (1.60-fold difference vs no HDPs). Phenome-wide MR analyses identified 37 unique non-HDP-related protein-disease associations, suggesting potential on-target effects associated with interventions lowering HDP risk through the identified proteins.

Conclusions and Relevance

Study findings suggest genetic associations of 4 cardiovascular disease-related proteins with gestational hypertension and 2 associated with preeclampsia. Future studies are required to test the efficacy of targeting the corresponding pathways to reduce HDP risk.

The CD94/NKG2A inhibitory receptor educates uterine NK cells to optimize pregnancy outcomes in humans and mice

The conserved CD94/NKG2A inhibitory receptor is expressed by nearly all human and ∼50% of mouse uterine natural killer (uNK) cells. Binding human HLA-E and mouse Qa-1, NKG2A drives NK cell education, a process of unknown physiological importance influenced by HLA-B alleles. Here, we show that NKG2A genetic ablation in dams mated with wild-type males caused suboptimal maternal vascular responses in pregnancy, accompanied by perturbed placental gene expression, reduced fetal weight, greater rates of smaller fetuses with asymmetric growth, and abnormal brain development. These are features of the human syndrome pre-eclampsia. In a genome-wide association study of 7,219 pre-eclampsia cases, we found a 7% greater relative risk associated with the maternal HLA-B allele that does not favor NKG2A education. These results show that the maternal HLA-B→HLA-E→NKG2A pathway contributes to healthy pregnancy and may have repercussions on offspring health, thus establishing the physiological relevance for NK cell education.

Video Abstract

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CD94/NKG2A educates uterine NK cells

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NKG2A-deficient dams display reduced utero-placental hemodynamic adaptations

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Asymmetric growth restriction and abnormal brain development in NKG2A-deficient dams

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Non-functional HLA-B→HLA-E→NKG2A pathway exposes women to greater pre-eclampsia risk

Preeclampsia Is a Syndrome with a Cascade of Pathophysiologic Events

This review integrates the currently available information on the molecular, cellular, and systemic mechanisms involved in the pathophysiology of preeclampsia. It highlights that the growth, protection, and promotion of the conceptus requires the modulation of an intact maternal immune system, communication between the mother and fetus, and adaptation of the maternal organic functions. A malfunction in any of these factors, on either side, will result in a failure of the cascade of events required for the normal course of pregnancy. Maladaptive processes, initially aiming to protect the conceptus, fail to anticipate the gradually increasing cardiovascular volume load during the course of pregnancy. As a result, multiple organ dysfunctions install progressively and eventually reach a state where mother and/or fetus are at risk of severe morbidity or even mortality, and where the termination of pregnancy becomes the least harmful solution. The helicopter view on pathophysiologic processes associated with preeclampsia, as presented in this paper, illustrates that the etiology of preeclampsia cannot be reduced to one single mechanism, but is to be considered a cascade of consecutive events, fundamentally not unique to pregnancy.

Combination of Genetic Markers and Age Effectively Facilitates the Identification of People with High Risk of Preeclampsia in the Han Chinese Population

Objective

This study aimed to analyze the possible association between known genetic risks and preeclampsia in a Han Chinese population.

Methods

A total of 156 patients with preeclampsia and 286 healthy Han Chinese women were enrolled and genotyped for 27 genetic alleles associated with preeclampsia in different populations. The association between the genotypes of the individual alleles and preeclampsia and the possible interaction among the alleles were analyzed. Finally logistic models were trained with the genotypes of possible alleles contributing to preeclampsia.

Results

Seven alleles were significantly or marginally significantly associated with preeclampsia, which involved six genes (rs4762 in AGT, rs1800896 in IL-10, rs1800629 and rs1799724 in TNFα, rs2070744 in NOS3, rs7412 in APOE, and rs2549782 in ERAP2). A multilocus interaction analysis further disclosed an interaction among seven alleles. A logistic model showing individual or synergetic contribution to preeclampsia could reach ~0.67 preeclampsia prediction accuracy in the Han Chinese population, while integration of age information could improve the performance to ~0.75 accuracy using a fivefold training-testing evaluation strategy.

Conclusions

The genetic factors were closely associated with preeclampsia in the Han Chinese population despite large ethnicity heterogeneity. The genotypes of different alleles also had synergetic interactions.

Inherited factors contribute to an inverse association between preeclampsia and breast cancer

Background

Preeclampsia is frequently linked to reduced breast cancer risk. However, little is known regarding the underlying genetic association and the association between preeclampsia and mammographic density.

Methods

This study estimates the incidence rate ratios (IRRs) of breast cancer in patients with preeclampsia, when compared to women without preeclampsia, using Poisson regression models in two cohorts of pregnant women: a Swedish nationwide cohort (n = 1,337,934, 1973–2011) and the Karolinska Mammography Project for Risk Prediction of Breast Cancer (KARMA, n = 55,044, 1958–2015). To identify the genetic association between preeclampsia and breast cancer, we used logistic regression models to calculate the odds ratios (ORs) of preeclampsia in sisters of breast cancer patients, and in women with different percentiles of breast cancer polygenic risk scores (PRS). Linear regression models were used to estimate the mammographic density by preeclampsia status in the KARMA cohort.

Results

A decreased risk of breast cancer was observed among patients with preeclampsia in both the nationwide (IRR = 0.90, 95% CI = 0.85; 0.96) and KARMA cohorts (IRR = 0.75, 95% CI = 0.61; 0.93). Women with high breast cancer PRS and sisters of breast cancer patients had a lower risk of preeclampsia (OR = 0.89, 95% CI = 0.83; 0.96). Mammographic density was lower in women with preeclampsia compared to women without preeclampsia (-2.04%, 95% CI = -2.65; -1.43). Additionally, among sisters in the KARMA cohort (N = 3500), density was lower in sisters of patients with preeclampsia compared to sisters of women without preeclampsia (-2.76%, 95% CI = -4.96; -0.56).

Conclusion

Preeclampsia is associated with reduced risk of breast cancer and mammographic density. Inherited factors contribute to this inverse association.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-017-0930-6) contains supplementary material, which is available to authorized users.

A Family Based Study of Carbon Monoxide and Nitric Oxide Signalling Genes and Preeclampsia

BACKGROUND

Preeclampsia is thought to originate during placentation, with incomplete remodelling and perfusion of the spiral arteries leading to reduced placental vascular capacity. Nitric oxide (NO) and carbon monoxide (CO) are powerful vasodilators that play a role in the placental vascular system. Although family clustering of preeclampsia has been observed, the existing genetic literature is limited by a failure to consider both mother and child.

METHODS

We conducted a nested case-control study within the Norwegian Mother and Child Birth Cohort of 1545 case-pairs and 995 control-pairs from 2540 validated dyads (2011 complete pairs, 529 missing mother or child genotype). We selected 1518 single-nucleotide polymorphisms (SNPs) with minor allele frequency >5% in NO and CO signalling pathways. We used log-linear Poisson regression models and likelihood ratio tests to assess maternal and child effects.

RESULTS

One SNP met criteria for a false discovery rate Q-value <0.05. The child variant, rs12547243 in adenylate cyclase 8 (ADCY8), was associated with an increased risk (relative risk [RR] 1.42, 95% confidence interval [CI] 1.20, 1.69 for AG vs. GG, RR 2.14, 95% CI 1.47, 3.11 for AA vs. GG, Q = 0.03). The maternal variant, rs30593 in PDE1C was associated with a decreased risk for the subtype of preeclampsia accompanied by early delivery (RR 0.45, 95% CI 0.27, 0.75 for TC vs. CC; Q = 0.02). None of the associations were replicated after correction for multiple testing.

CONCLUSIONS

This study uses a novel approach to disentangle maternal and child genotypic effects of NO and CO signalling genes on preeclampsia.

Cohort profile: the Finnish Genetics of Pre-eclampsia Consortium (FINNPEC)

PURPOSE

The Finnish Genetics of Pre-eclampsia Consortium (FINNPEC) Study was established to set up a nationwide clinical and DNA database on women with and without pre-eclampsia (PE), including their partners and infants, in order to identify genetic risk factors for PE.

PARTICIPANTS

FINNPEC is a cross-sectional case-control cohort collected from 5 university hospitals in Finland during 2008-2011. A total of 1450 patients with PE and 1065 pregnant control women without PE (aged 18-47 years) were recruited. Altogether, there were 1377 full triads (625 PE and 752 control triads).

FINDINGS TO DATE

The established cohort holds both clinical and genetic information of mother-infant-father triads representing a valuable resource for studying the pathogenesis of the disease. Furthermore, maternal biological samples (first and third trimester serum and placenta) will provide additional information for PE research. Until now, research has encompassed studies on candidate genes, Sanger and next-generation sequencing, and various studies on the placenta. FINNPEC has also participated in the InterPregGen study, which is the largest investigation on maternal and fetal genetic factors underlying PE until now.

FUTURE PLANS

Ongoing studies focus on elucidating the role of immunogenetic and metabolic factors in PE. Data on morbidity and mortality will be collected from mothers and fathers through links to the nationwide health registers.

An RGS2 3'UTR polymorphism is associated with preeclampsia in overweight women

BACKGROUND

Preeclampsia is a common and heterogeneous vascular syndrome of pregnancy. Its genetic risk profile is yet unknown and may vary between individuals and populations. The rs4606 3' UTR polymorphism of the Regulator of G-protein signaling 2 gene (RGS2) in the mother has been implicated in preeclampsia as well as in the development of chronic hypertension after preeclampsia. The RGS2 protein acts as an inhibitor of physiological vasoconstrictive pathways, and a low RGS2 level is associated with hypertension and obesity, two conditions that predispose to preeclampsia. We genotyped the rs4606 polymorphism in 1339 preeclamptic patients and in 697 controls from the Finnish Genetics of Preeclampsia Consortium (FINNPEC) cohort to study the association of the variant with preeclampsia.

RESULTS

No association between rs4606 and preeclampsia was detected in the analysis including all women. However, the polymorphism was associated with preeclampsia in a subgroup of overweight women (body mass index ≥ 25 kg/m(2), and < 30 kg/m(2)) (dominant model; odds ratio, 1.64; 95 % confidence interval, 1.10-2.42).

CONCLUSIONS

Our results suggest that RGS2 might be involved in the pathogenesis of preeclampsia particularly in overweight women and contribute to their increased risk for hypertension and other types of cardiovascular disease later in life.

Exome sequencing in pooled DNA samples to identify maternal pre-eclampsia risk variants

Pre-eclampsia is a common pregnancy disorder that is a major cause for maternal and perinatal mortality and morbidity. Variants predisposing to pre-eclampsia might be under negative evolutionary selection that is likely to keep their population frequencies low. We exome sequenced samples from a hundred Finnish pre-eclamptic women in pools of ten to screen for low-frequency, large-effect risk variants for pre-eclampsia. After filtering and additional genotyping steps, we selected 28 low-frequency missense, nonsense and splice site variants that were enriched in the pre-eclampsia pools compared to reference data, and genotyped the variants in 1353 pre-eclamptic and 699 non-pre-eclamptic women to test the association of them with pre-eclampsia and quantitative traits relevant for the disease. Genotypes from the SISu project (n = 6118 exome sequenced Finnish samples) were included in the binary trait association analysis as a population reference to increase statistical power. In these analyses, none of the variants tested reached genome-wide significance. In conclusion, the genetic risk for pre-eclampsia is likely complex even in a population isolate like Finland, and larger sample sizes will be necessary to detect risk variants.